Bones and Disorders of Connective Tissue

Structure and Functions of Bone Tissues

PHARM. EMERENCIANA M. JAMES

Definition Of Bone

• Bone is a hard and rigid tissue that forms the bony skeleton of the body.
• Bone supports the body weight,
• It provides attachment to muscles,
• Acts as lever for movements, and

provides protection to organs

Inside the bone there are spaces, which are filled with the bone marrow that produce red blood cells, platelets and cells of the immune system

Bones and Disorders of Connective Tissue

Cells of the immune system produced in bone marrow include monocytes, lymphocytes, mast cells, neutrophils, eosinophils and basophils The only difference with other connective tissues is that its ground substance is made up of inorganic salts, mostly calcium ions The bone is highly vascularized, and in living conditions the bone appears pinkish in colour

Bone consists of:

• Cells
• Fibers

Ground substances

Bone Cells; The bone contains four types of cells namely the osteoprogenator cells, osteoblasts, osteocytes, and the osteoclasts

Bone Matrix (Intercellular substance);It is made up of the collagen fibers (osteocollagenous fibers), amorphous ground substance and inorganic salts which constitute about 74% of bone mass

Types of Bones

• Long bones e.g. femur, tibia and fibula
• Short bones e.g. carpals (wrist bones)
• Flat bones e.g. sternum, ribs and most skull bones (skull)
• Irregular bones e.g. vertebrae and some skull bones

Sesamoid bones e.g. patella (kneecap)

Parts of the long bone

• A long bone is one that has greater length than width.

A typical long bone consists of the following parts:

The diaphysis is the bone’s shaft or body—the long, cylindrical, main portion of the bone.

The epiphyses (singular is epiphysis) are the proximal and distal ends of the bone.

The metaphyses (singular is metaphysis) are the regions between the diaphysis and the epiphyses.

Bones Formation

• Bones formation is commonly referred to as ossification and it occurs in two processes

Intramembranous Ossification

The bones that form by this process include most of skull bones such as frontal,parietal, maxilla, mandible, clavicle and parts of occipital and temporal bones.

Endochondral Ossification

In endochondral ossification bone is formed from the pre-existing hyaline cartilage that has the shape that closely resembles the bone to be formed.

Bones and Disorders of Connective Tissue

Most long and irregular bones form via endochondral ossification, such as the base of the skull, vertebral column, the pelvis and bones of the extremities (limbs).

• During this process the cartilage is gradually replaced by bone.
• Only a small amount of cartilage remains covering the articular surfaces of the joints.

During endochondral ossification the bone also grows in length and width.

Generally flat bones develop by intramembranous ossification while long bones develop by intra cartilaginous ossification

Bones formation occurs in four main stages which are

• Development of the ossification canters (special membrane)
• Formation of bone matrix
• Deposition of minerals or calcification

Formation of trabeculae and appearance of periosteum

Functions of Bones

Support

The skeleton serves as the structural framework for the body by supporting soft tissues providing attachment points for the tendons of most skeletal muscles Protection

The skeleton protects the most important internal organs from injury for example, cranial bones protect the brain, vertebrae (backbones) protect the spinal cord, and the ribcage protects the heart and lungs.

Movement

• When muscles contract, they pull on bones to produce movement.

Mineral homeostasis (storage and release);

Bone tissue stores several minerals, especially calcium and phosphorus, which contribute to the strength of bone Blood cell production;

bone marrow produces red blood cells, white blood cells, and platelets, a process called hemopoiesis

KEYPOINTS

• Bone is a hard and rigid connective tissue that forms the bony skeleton of the body
• Functions of bones
• Bone supports the body weight,
• It provides attachment to muscles,
• Acts as lever for movements, and provides protection to organs.
• Inside the bone there are spaces, which are filled with the bone marrow that produce

Red blood cells, platelets and cells of the immune system.

Production of body cells: monocytes, lymphocytes, mast cells, neutrophils, eosinophils and basophils

QUESTIONS

• What is bone tissue?
• What are the types of bones?

What are the functions of bones?

Common Disorders of

Connective Tissues

PHARM. EMERENCIANA M. JAMES

Common Disorders of Connective Tissues

A connective tissue diseases are diseases that affect the joints (parts of the body that connect the structures of the body together).

• It is presented by the inflammation of the joints (arthritis)

It may be infective or non-infective.

In most cases, all signs of inflammation are present (swollen joints, hot, tender and red) and there is limitation of movements

Common Types of Connective Tissue Diseases

• Acute pyrogenic arthritis
• Gout
• Chronic joint disease
• Osteoarthritis
• Generalized bone disease
• Osteomalacia

Osteoporosis

Acute pyrogenic arthritis

• This is the infection of the joints by pus-producing bacteria

It is caused by any pyrogenic bacteria like staphylococci.

The infection may start suddenly without any obvious cause or may occur from other septic focus nearby like osteomyelitis The patients complain of pain, swelling and reduced movement of the joint

Gout

This is arthritis due to congenital abnormality of uric acid metabolism, leading to abnormal high uric acid in the blood.

• Uric acid is deposited in joints and also around the joints and in the ear cartilages.

The kidney may be damaged and kidney stones may form in them.

The disease is commonest in men over 40 years.

The acute episodes may be precipitated by alcohol excess, surgery, infections or treatment with thiazide diuretics which raise serum uric acid even in normal people.

Patients experience irritability and malaise a day or two before acute attack of gout and sudden severe pain starts in one joint especially that of big toe

Chronic joint disease

• Rheumatoid arthritis

The cause is thought to be abnormal immunological reactions.

Women are affected then men at the age between 20 – 40 years and psychological factors are often involved.

The patient notices pain and stiffness of a joint, then swollen joints and finally radiate to the wrist, knee and hips

Osteoarthritis

• This is due to a degeneration of the articular cartilage of joints.

It is common to older people.

The exact cause is not certain but it comes with age particularly in people who have done heavy work.

It also occurs after injuries that have involved a joint or bone.

The only symptom is aching pain in the joints, worse at the end of the day and relieved by rest.

Generalized bone disease

• Osteoporosis

It is a condition in which the bones are thinned though their composition is normal.

It can be caused by immobilization; when a limb is put in plaster or stay in bed for a long time, menopause in women, old age, Cushing’s syndrome and steroid treatment.

The pain occurs only when there is bone fracture.

Osteomalacia

• This is a different form of weakening of bones due to vitamin D deficiency.
• It is common in adults.
• There are bone pains, often muscular weakness and may be tetany.

The weakened bones may collapse and deform.